The present invention relates generally to manipulators. More particularly, the present invention relates to manipulators that comprise part grips, such as vacuum gripper cups, and a unique rotary union for safe, 360 degree rotation of large, heavy objects and translation along 2 axes.
It is often necessary to lift and manipulate large, heavy objects during a manufacturing process, such as, for example, during the process of welding steel enclosures (known as xe2x80x9ctanksxe2x80x9d) for transformers, particularly pad-mounted transformers. These large, usually rectangular tanks can be automatically welded or welded by hand.
In electrical power distribution systems, distribution transformers are used to step down voltage between the high voltage power line and the user. Transformers are typically mounted above ground on a junction pole, or at ground level on a pad or platform. The increased use of underground power distribution systems has resulted in a corresponding increase in the number of pad-mounted transformers. The transformer includes a tank, which contains the core and coil assembly immersed in oil, and a cabinet, which includes a top hinged door and a bolted in place sill. Connections for incorporating the transformer assembly into the power distribution system extend through one wall of the tank and are enclosed by the cabinet. In order to provide utility personnel the necessary access to the transformer connections, the cabinet must also include a door. The cabinet door is pivotally attached to the tank along the top edge of the front plate of the tank. The cabinet also includes a low sill extending forward from the transformer tank, upon which the cabinet door rests when closed.
Transformer enclosures are generally fabricated from two to four metal sheets. The sheet material for these tanks are generally less than 10-gauge carbon steel or 10-gauge stainless steel. However, other kinds and gauges of metals may be used depending upon customer requirements. It is important that the method of fabrication for these enclosures be flexible enough to accommodate the broad range of enclosures that are fabricated in the transformer assembly line. The geometry of these enclosures is typically a three-dimensional box, i.e., cube-shaped or rectangular parallelepiped-shaped, but can also be extended to other shapes such as cylinders. The dimensions of the sheets that comprise these enclosures vary depending upon customer requirements. For example, a rectangular parallelepiped-shaped transformer enclosure generally comprises a front panel, a tank wrapper, a door wrapper, and a door top.
The metal sheets that comprise the transformer tanks are typically mated together in a series of welds to form a six-sided enclosure. The seam welding of the various panels that comprise the transformer tank is typically performed by an automated assembly process, such as via a robotic welder. Further welds are needed to join or affix additional parts or components to the tanks. Additional hardware or components are welded onto one or more sides of the enclosure via manual welding. The welding of components is more suitable for manual welding due to the varying locations (i.e., interior or exterior surfaces, horizontal or vertical surfaces) for these components and the size and location of the welds.
For typical transformer enclosures, hardware is manually welded onto four of the six sides of the enclosure via conventional welding processes known in the art such as tungsten inert gas (TIG) welding and metal inert gas (MIG) welding. The large and cumbersome metal enclosures can weigh in excess of several hundred pounds and are manipulated by hand on a roller bed conveyor or lift table. The components are welded onto the horizontal or vertical tank surfaces that are within reach of the operator. Once the weld on the particular surface is completed, the tank is rotated or flipped manually to present another surface for welding.
As a tank typically weighs more than 50 pounds (and frequently up to as much as 150 pounds or more), a tank is too heavy and too large for an ordinary person to move from the lift table or conveyor to the manual welding station, or vice versa, without the aid of a manipulator. Because of these difficulties in handling of the workpiece, this method increases the likelihood of occupational injuries. An additional drawback is operator fatigue. Operator fatigue increases as a result of manipulation of these enclosures over the course of many hours and can lead to an overall decrease in the efficiency of the manual welding process. Moreover, operator fatigue can also lead to an increase in quality problems in the manual welding process.
Other quality problems attributable to the manual welding process are related to the nature of the design of the enclosure. Welding of a horizontal surface and then a vertical surface is generally not optimal for consistent welds. In conventional manual welding processes, the voltage and current of the welding arc determine the fluidity of the molten weld puddle. If the angle varies for the different components that are joined to the enclosure, the molten weld puddle may run faster or slower due to gravity thereby causing the size and shape of the weld to change. The current arrangement of settings at the manual welding stations are not adjustable for each new weld surface and may alter the quality of the welds. Thus, there is a need in the art for a manipulator that may be incorporated into the manual welding workstation that can aid a person in lifting and manipulating large, heavy objects, while translating the object along 2 axes and rotating the objects up to 360 degrees on two different axes to expose new weld surfaces.
The present invention overcomes difficulties in the handling and manipulation of large, cumbersome objects, such as transformer tank enclosures, by providing manipulators and apparatuses for safe, 360 degree, 2 axis rotation and translation of large, heavy objects. The apparatuses of the present invention allow an operator to safely and easily manipulate the work piece by minimizing contact with the tank. The manipulator of the present invention affords the operator the flexibility to position any of the surfaces of the work piece to an optimal height and angle to be worked upon. Furthermore, the manipulator of the present invention reduces the physical exertion required by the operator to lift, position, and orient the tanks that weigh upwards of about 150 pounds thereby minimizing injuries to the operator. Lastly, the manipulator of the present invention is adjustable to accommodate the height of the operator as well as the dimensions of the work pieces.
The manipulator of the present invention is comprised of a framework that supports a rotatable, inner frame assembly that is joined to a hoist that is mounted onto a carriage. The inner frame assembly engages the object or work piece and holds it in place. The inner frame assembly comprises a support member which can be mounted either horizontally or vertically. The support member further comprises a plurality of extension arms that are located at opposite ends of the support member. These extension arms comprise a plurality of rotary shafts that terminate with one or more part grips that engage the object or work piece. The part grips preferably engage the object at opposing surfaces of the object, near or at the object""s center of gravity. The part grips may engage the object through the use of vacuum, magnetic, mechanical, or similar means to securely hold the object. In preferred embodiments, the part grips are gripper cups in which a vacuum is drawn against the surfaces of the object thereby holding it in place.
The rotary shafts, disposed at the end of the extension arms on the inner frame assembly, allow the operator to rotate the object forward or backward, preferably along the axis of the part grips. The rotary shafts are comprised of one or more bearings and rotary actuators in which the operator can rotate the object forward and backward 360xc2x0 along a horizontal axis with minimal effort. In preferred embodiments, the rotary shafts further comprise one or more brakes to hold the object in position while the operator is working on the surface of the object.
The object can be further manipulated through the use of a shaft attached to the top surface of the support member on the inner frame assembly, preferably substantially in the center axis of the support member. The shaft is preferably parallel to the orientation of the extension arms. For example, in embodiments where the extension arms are horizontal, the shaft is also horizontal whereas in other embodiments where the extension arms are vertical, the shaft is also vertical. This shaft further comprises a rotary union that allows the passage of air, vacuum, or other means to operate various actuators, brakes, and holders associated with the inner frame assembly. In embodiments where the shaft is horizontal, the object can be rotated horizontally 360xc2x0 clock-wise about the axis of the central shaft. In other embodiments where the shaft is vertical, the object can be rotated vertically 360xc2x0 about the axis of the central shaft. One or more actuators and one or more brakes facilitate the movement and stoppage of the object as it is being rotated about the central axis of the shaft.
The inner frame assembly and work piece connected thereto, can translate vertically and horizontally by means of a carriage assembly that further comprises a hoist. The carriage assembly preferably travels upon rails located at the top of the framework. A hoist, such as, but not limited to, a pneumatic hoist or air hoist, engages the inner frame assembly and object connected thereto to allow the operator to vertically adjust the height of the object. The carriage assembly further comprises a handle that contains controls to operate the hoist as well as allow the operator to horizontally translate the inner frame assembly from a first position to a second position. The carriage assembly and open framework is further comprised of a plurality of bearings that allow the interior frame assembly, and object or work piece contained therein, to translate linearly, preferably vertically, from a first position to a second position. The operator can then operate the hoist to raise and lower the inner frame assembly and work piece attached thereto. In some embodiments in which the inner frame assembly is oriented horizontally, the inner frame assembly is mounted onto a yoke assembly which is connected to the hoist by a linkage, such as a cable. The yoke assembly engages bearings or linear motion blocks on the side of support beams attached to the carriage to facilitate vertical translation.